Small Engines (Lawn Mowers, etc.): Honda self-propelled mulching lawnmower, cycle engines, loud pop

Question
I have a Honda self-propelled mulching lawnmower, which is two years old.  I mowed about 3/4 of my yard, took a break, then tried to start the mower again but I felt great resistance when I tried to pull the start cord.  Usually, it's very easy to pull and start (will start with one pull).  After trying to pull it a few times, I heard a very loud pop, like a firecracker (backfire). Needless to say, it won't start.  Is there something I can do to fix this problem?  Thanks.

Answer
First, remove the spark plug.  See if you can pull the string.  Is the oil level correct?  If so, replace the spark plug with a brand new one and see if it starts.
It's rare for 4 cycle engines, especially Honda's, to foul spark plugs but I have seen this a few times.
Let me know what happens.
Eroc